The first test ride was not too successful. The range metering worked pretty well; however, the connection between phone and raspberry pi was crashing very often. And when this happened, the data logging stopped as well. It would be great to simplify the setup. When the arduino could log the data directly, a lot of problems would be solved.
So I started looking for a solution and found a nice data logging shield from adafruit. It uses a SD card to write the data. With this, I could skip the raspberry pi completely.
Now I will have to wait a bit until the shield arrives.